The present invention relates generally to tier management and, more particularly, to a method and an apparatus of data location management.
In recent years, thin provisioning has become popular. Thin provisioning is a method for allocating area for a storage system that receives a write command to an unallocated area and allocates physical devices in response to the write commands. Storage systems may also reallocate frequently accessed allocated area to fast and expensive media and rarely accessed allocated area to slow and cheap media. Generally, when a storage system receives a write command to an unallocated area, the storage system allocates a default tier area to the unallocated area.
An application program uses flash memory drive on server as a cache in order to increase performance. The application program reads data from the flash memory drive instead of the storage subsystem if there is the data on the flash memory drive and writes the data to the flash memory drive and the storage subsystem. However, there is flash memory device on the storage subsystem and frequently written areas in storage subsystem are moved to a higher tier that is the flash memory device. Therefore, the frequently written areas are located on the flash memory drive on the server and the flash memory device on the storage subsystem. Further, frequently accessed areas cannot be moved to a higher tier and performance will decrease.
According to US2011/0202705, an administrator can locate a specified volume to a specified tier. However, the storage subsystem cannot know whether a volume copy command from the management server is for deploy or backup. Therefore, the storage subsystem cannot locate the volume to an applicable tier. According to US2009/0144496 A1, the storage controller can compress virtual volumes by a page.